1. Field of the Invention
Numerous deposit-forming substances are inherent in hydrocarbon fuels. These substances, when used in internal combustion engines, tend to form deposits on and around constricted areas of the engine contacted by the fuel. Typical areas commonly and sometimes seriously burdened by the formation of deposits include carburetor ports, the throttle body and venturies, engine intake valves, etc.
Deposits adversely affect the operation of the vehicle. For example, deposits on the carburetor throttle body and venturies increase the fuel to air ratio of the gas mixture to the combustion chamber thereby increasing the amount of unburned hydrocarbon and carbon monoxide discharged from the chamber. The high fuel-air ratio also reduces the gas mileage obtainable from the vehicle.
Deposits on the engine intake valves when they get sufficiently heavy, on the other hand, restrict the gas mixture flow into the combustion chamber. This restriction, starves the engine of air and fuel and results in a loss of power. Deposits on the valves also increase the probability of valve failure due to burning and improper valve seating. In addition, these deposits may break off and enter the combustion chamber possibly resulting in mechanical damage to the piston, piston rings, engine head, etc.
The formation of these deposits can be inhibited as well as removed by incorporating an active detergent into the fuel. These detergents function to cleanse these deposit-prone areas of the harmful deposits, thereby enhancing engine performance and longevity. There are numerous detergent-type gasoline additives currently available which, to varying degrees, perform these functions.
The use of detergent-type gasoline additives is complicated by a phenomenon termed "Octene Requirement Increase "("ORI"). In particular, with regard to automobile engines that require the use of nonleaded gasolines (to prevent disablement of catalytic converters used to reduce emissions), it has been found difficult to provide gasoline of high enough octane to prevent knocking and the concomitant damage which it causes. The chief problem lies in the area of the degree of octane requirement increase, herein called "ORI", which is caused by deposits formed by the commercial gasoline.
The basis of the ORI problem is as follows: each engine, when new, requires a certain minimum octane fuel in order to operate satisfactorily without pinging and/or knocking. As the engine is operated on any gasoline, this minimum octane increases and, in most cases, if the engine is operated on the same fuel for a prolonged period, will reach an equilibrium. This is apparently caused by an amount of deposits in the combustion chamber. Equilibrium is typically reached after 5,000 to 15,000 miles of automobile operation.
The octane requirement increase in particular engines used with commercial gasolines will vary at equilibrium from 5 to 6 octane units to as high as 12 or 15 units, depending upon the gasoline compositions, engine design and type of operation. The seriousness of the problem is thus apparent. A typical automobile with a research octane requirement of 85, when new, may after a few months of operation require 97 research octane gasoline for proper operation, and little unleaded gasoline of that octane is available. The ORI problem also exists in some degree with engines operated on leaded fuels. U.S. Pat. Nos. 3,144,311; 3,146,203; and 4,247,301 disclose lead-containing fuel compositions having reduced ORI properties.
The ORI problem is compounded by the fact that the most common method for increasing the octane rating of unleaded gasoline is to increase its aromatic content. This, however, eventually causes an even greater increase in the octane requirement.
This ORI problem is recognized to be particularly significant with fuels, especially unleaded fuels, containing hydrocarbyl-substituted polyamine fuel additives. Accordingly, while certain hydrocarbyl-substituted polyamine additives are well known in the art as excellent dispersant/detergent fuel additives which have been commercially successful in leaded gasolines, the ORI problem associated with these additives have prevented their commercial use in unleaded gasolines. Accordingly, it would be particularly advantageous to develop a fuel composition containing such hydrocarbyl-substituted polyamine additives which would reduce to an acceptable level the ORI associated with these additives.
The instant invention is directed to synergistic fuel compositions containing a hydrocarbyl-substituted amine or polyamine and a hydrocarbyl-terminated poly(oxyalkylene) monool. These compositions provide for an unexpected decrease in those deposits which have been correlated to ORI.
2. Prior Art
Hydrocarbyl-substituted polyamines useful as fuel additives are known in the art and are disclosed in U.S. Pat. Nos. 3,438,757; 3,565,804; 3,574,576; and 3,671,511.
Likewise, the use of poly(oxyalkylene) diols as an additive in fuel compositions is disclosed in U.S. Pat. No. 4,548,616 which discloses the use of block copolymers as an ORI additive. U.S. Pat. No. 3,756,793 discloses fuel compositions containing a combination of a hydrocarbyl polyamine with a polyether glycol and etherified and esterfied products thereof.
U.S. Pat. No. 4,160,648 discloses certain polyether carbamates as fuel additives possessing good ORI properties and further discloses that poly(oxyalkylene) monools and polyols display synergistic effects when combined with such polyether carbamates in fuel compositions.
However, these references neither disclose the combination of hydrocarbyl-substituted polyamines with a C.sub.1 -C.sub.30 hydrocarbyl-terminated poly(oxyalkylene) monool nor do any of these references teach that such a combination would synergistically result in lower ORI for such fuel compositions.